[AltServer] Suggests disabling “Offload Unused Apps” in error message

iOS 13.5 counts offloaded apps as active sideloaded apps (for some reason), so improve error messages to mention this.

AltKit/CodableServerError.swift

@@ -30,7 +30,13 @@ struct CodableServerError: Codable
     {
         self.errorCode = error.code
         
-        let userInfo = error.userInfo.compactMapValues { $0 as? String }
+        var userInfo = error.userInfo.compactMapValues { $0 as? String }
+        
+        if let localizedRecoverySuggestion = (error as NSError).localizedRecoverySuggestion
+        {
+            userInfo[NSLocalizedRecoverySuggestionErrorKey] = localizedRecoverySuggestion
+        }
+        
         if !userInfo.isEmpty
         {
             self.userInfo = userInfo

AltKit/NSError+ALTServerError.m

@@ -112,6 +112,9 @@ NSErrorUserInfoKey const ALTProvisioningProfileBundleIDErrorKey = @"bundleIdenti
         case ALTServerErrorPluginNotFound:
             return NSLocalizedString(@"Make sure Mail is running and the plug-in is enabled in Mail's preferences.", @"");
             
+        case ALTServerErrorMaximumFreeAppLimitReached:
+            return NSLocalizedString(@"Make sure “Offload Unused Apps” is disabled in Settings > iTunes & App Stores, then install or delete all offloaded apps.", @"");
+            
         default:
             return nil;
     }

AltServer/AppDelegate.swift

@@ -212,6 +212,10 @@ private extension AppDelegate
                     {
                         alert.informativeText = underlyingError.localizedDescription
                     }
+                    else if let recoverySuggestion = error.localizedRecoverySuggestion
+                    {
+                        alert.informativeText = error.localizedDescription + "\n\n" + recoverySuggestion
+                    }
                     else
                     {
                         alert.informativeText = error.localizedDescription